Map
// empty map container
map<int, int> gquiz1;
// insert elements in random order
gquiz1.insert(pair<int, int>(1, 40));
gquiz1.insert({1,40});
// printing map gquiz1
map<int, int>::iterator itr;
for (itr = gquiz1.begin(); itr != gquiz1.end(); ++itr) {
cout << '\t' << itr->first
<< '\t' << itr->second << '\n';
}
// assigning the elements from gquiz1 to gquiz2
map<int, int> gquiz2(gquiz1.begin(), gquiz1.end());
// remove all elements up to
// element with key=3 in gquiz2
cout << "\ngquiz2 after removal of"
" elements less than key=3 : \n";
cout << "\tKEY\tELEMENT\n";
gquiz2.erase(gquiz2.begin(), gquiz2.find(3));
// remove all elements with key = 4
int num;
num = gquiz2.erase(4);
// lower bound and upper bound for map gquiz1 key = 5
cout << "gquiz1.lower_bound(5) : "
<< "\tKEY = ";
cout << gquiz1.lower_bound(5)->first << '\t';
cout << "\tELEMENT = "
<< gquiz1.lower_bound(5)->second << endl;
cout << "gquiz1.upper_bound(5) : "
<< "\tKEY = ";
cout << gquiz1.upper_bound(5)->first << '\t';
cout << "\tELEMENT = "
<< gquiz1.upper_bound(5)->second << endl;
// sort map by its member
sort(v.begin(),v.end(),comparator)
bool comparator(mem i1, mem i2)
{
return (i1.first < i2.first) }
// initialize container; copy constructor
map<int, int> mp, copymp;
// insert elements in random order
mp.insert({ 2, 30 });
mp.insert({ 1, 40 });
mp.insert({ 4, 50 });
h[{y, x}].insert(root->val);
// = operator is used to copy map
copymp = mp;
Set
#include <iostream>
#include <set>
#include <iterator>
using namespace std;
int main()
{
// empty set container
set <int, greater <int> > gquiz1;
// insert elements in random order
gquiz1.insert(40);
gquiz1.insert(30);
gquiz1.insert(60);
gquiz1.insert(20);
gquiz1.insert(50);
gquiz1.insert(50); // only one 50 will be added to the set
gquiz1.insert(10);
// printing set gquiz1
set <int, greater <int> > :: iterator itr;
cout << "\nThe set gquiz1 is : ";
for (itr = gquiz1.begin(); itr != gquiz1.end(); ++itr)
{
cout << '\t' << *itr;
}
cout << endl;
// assigning the elements from gquiz1 to gquiz2
set <int> gquiz2(gquiz1.begin(), gquiz1.end());
// print all elements of the set gquiz2
cout << "\nThe set gquiz2 after assign from gquiz1 is : ";
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
{
cout << '\t' << *itr;
}
cout << endl;
// remove all elements up to 30 in gquiz2
cout << "\ngquiz2 after removal of elements less than 30 : ";
gquiz2.erase(gquiz2.begin(), gquiz2.find(30));
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
{
cout << '\t' << *itr;
}
// remove element with value 50 in gquiz2
int num;
num = gquiz2.erase (50);
cout << "\ngquiz2.erase(50) : ";
cout << num << " removed \t" ;
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
{
cout << '\t' << *itr;
}
cout << endl;
//lower bound and upper bound for set gquiz1
cout << "gquiz1.lower_bound(40) : "
<< *gquiz1.lower_bound(40) << endl;
cout << "gquiz1.upper_bound(40) : "
<< *gquiz1.upper_bound(40) << endl;
//lower bound and upper bound for set gquiz2
cout << "gquiz2.lower_bound(40) : "
<< *gquiz2.lower_bound(40) << endl;
cout << "gquiz2.upper_bound(40) : "
<< *gquiz2.upper_bound(40) << endl;
return 0;
}
Erase Function
set.erase(position)
set.erase(startingposition, endingposition)
erase(iterator, iterator)
erase(element) --> return its index;
Stack
// CPP program to demonstrate working of STL stack
#include <iostream>
#include <stack>
using namespace std;
void showstack(stack <int> s)
{
while (!s.empty())
{
cout << '\t' << s.top();
s.pop();
}
cout << '\n';
}
int main ()
{
stack <int> s;
s.push(10);
s.push(30);
s.push(20);
s.push(5);
s.push(1);
cout << "The stack is : ";
showstack(s);
cout << "\ns.size() : " << s.size();
cout << "\ns.top() : " << s.top();
cout << "\ns.pop() : ";
s.pop();
showstack(s);
return 0;
}
Deque
#include <iostream>
#include <deque>
using namespace std;
void showdq(deque <int> g)
{
deque <int> :: iterator it;
for (it = g.begin(); it != g.end(); ++it)
cout << '\t' << *it;
cout << '\n';
}
int main()
{
deque <int> gquiz;
gquiz.push_back(10);
gquiz.push_front(20);
gquiz.push_back(30);
gquiz.push_front(15);
cout << "The deque gquiz is : ";
showdq(gquiz);
cout << "\ngquiz.size() : " << gquiz.size();
cout << "\ngquiz.max_size() : " << gquiz.max_size();
cout << "\ngquiz.at(2) : " << gquiz.at(2);
cout << "\ngquiz.front() : " << gquiz.front();
cout << "\ngquiz.back() : " << gquiz.back();
cout << "\ngquiz.pop_front() : ";
gquiz.pop_front();
showdq(gquiz);
cout << "\ngquiz.pop_back() : ";
gquiz.pop_back();
showdq(gquiz);
return 0;
}
Queue
// CPP code to illustrate
// Queue in Standard Template Library (STL)
#include <iostream>
#include <queue>
using namespace std;
void showq(queue <int> gq)
{
queue <int> g = gq;
while (!g.empty())
{
cout << '\t' << g.front();
g.pop();
}
cout << '\n';
}
int main()
{
queue <int> gquiz;
gquiz.push(10);
gquiz.push(20);
gquiz.push(30);
cout << "The queue gquiz is : ";
showq(gquiz);
cout << "\ngquiz.size() : " << gquiz.size();
cout << "\ngquiz.front() : " << gquiz.front();
cout << "\ngquiz.back() : " << gquiz.back();
cout << "\ngquiz.pop() : ";
gquiz.pop();
showq(gquiz);
return 0;
}
Prioity_Queue
// this is an strucure which implements the
// operator overlading
struct CompareHeight {
bool operator()(Person const& p1, Person const& p2)
{
// return "true" if "p1" is ordered
// before "p2", for example: back is top!!!
return p1.height < p2.height;
}
};
int main()
{
priority_queue<Person, vector<Person>, CompareHeight> Q;
// When we use priority_queue with structure
// then we need this kind of syntax where
// CompareAge is the functor or comparision function
float arr[ROW][COL] = { { 30, 5.5 }, { 25, 5 },
{ 20, 6 }, { 33, 6.1 }, { 23, 5.6 } };
for (int i = 0; i < ROW; ++i) {
Q.push(Person(arr[i][0], arr[i][1]));
// insert an object in priority_queue by using
// the Person strucure constructor
}
while (!Q.empty()) {
Person p = Q.top();
Q.pop();
cout << p.age << " " << p.height << "\n";
}
return 0;
}
// C++ program to create a priority queue of pairs.
// By default a max heap is created ordered
// by first element of pair.
#include <bits/stdc++.h>
using namespace std;
// Driver program to test methods of graph class
int main()
{
// By default a max heap is created ordered
// by first element of pair.
priority_queue<pair<int, int> > pq;
pq.push(make_pair(10, 200));
pq.push(make_pair(20, 100));
pq.push(make_pair(15, 400));
pair<int, int> top = pq.top();
cout << top.first << " " << top.second;
return 0;
}
// C++ program to create a priority queue of pairs.
// We can create a min heap by passing adding two
// parameters, vector and greater().
#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pi;
// Driver program to test methods of graph class
int main()
{
// By default a min heap is created ordered
// by first element of pair.
priority_queue<pi, vector<pi>, greater<pi> > pq;
pq.push(make_pair(10, 200));
pq.push(make_pair(20, 100));
pq.push(make_pair(15, 400));
pair<int, int> top = pq.top();
cout << top.first << " " << top.second;
return 0;
}
// Note that by default C++ creates a max-heap
// for priority queue
#include <iostream>
#include <queue>
using namespace std;
void showpq(priority_queue <int> gq)
{
priority_queue <int> g = gq;
while (!g.empty())
{
cout << '\t' << g.top();
g.pop();
}
cout << '\n';
}
int main ()
{
priority_queue <int> gquiz; // 从小到大
gquiz.push(10);
gquiz.push(30);
gquiz.push(20);
gquiz.push(5);
gquiz.push(1);
priority_queue <int, vector<int>, greater<int>> gquiz; //从大到小
gquiz.push(10);
gquiz.push(30);
gquiz.push(20);
gquiz.push(5);
gquiz.push(1);
cout << "The priority queue gquiz is : ";
showpq(gquiz);
cout << "\ngquiz.size() : " << gquiz.size();
cout << "\ngquiz.top() : " << gquiz.top();
cout << "\ngquiz.pop() : ";
gquiz.pop();
showpq(gquiz);
return 0;
}
List
#include <iostream>
#include <list>
#include <iterator>
using namespace std;
//function for printing the elements in a list
void showlist(list <int> g)
{
list <int> :: iterator it;
for(it = g.begin(); it != g.end(); ++it)
cout << '\t' << *it;
cout << '\n';
}
int main()
{
list <int> gqlist1, gqlist2;
for (int i = 0; i < 10; ++i)
{
gqlist1.push_back(i * 2);
gqlist2.push_front(i * 3);
}
cout << "\nList 1 (gqlist1) is : ";
showlist(gqlist1);
cout << "\nList 2 (gqlist2) is : ";
showlist(gqlist2);
cout << "\ngqlist1.front() : " << gqlist1.front();
cout << "\ngqlist1.back() : " << gqlist1.back();
cout << "\ngqlist1.pop_front() : ";
gqlist1.pop_front();
showlist(gqlist1);
cout << "\ngqlist2.pop_back() : ";
gqlist2.pop_back();
showlist(gqlist2);
cout << "\ngqlist1.reverse() : ";
gqlist1.reverse();
showlist(gqlist1);
cout << "\ngqlist2.sort(): ";
gqlist2.sort();
showlist(gqlist2);
return 0;
}
String
string& string::insert (size_type idx, const string& str)
// CPP code for insert (size_type idx, const string& str)
#include <iostream>
#include <string>
using namespace std;
// Function to demonstrate insert
void insertDemo(string str1, string str2)
{
// Inserts str2 in str1 starting
// from 6th index of str1
str1.insert(6, str2);
cout << "Using insert : ";
cout << str1;
}
// Driver code
int main()
{
string str1("Hello World! ");
string str2("GeeksforGeeks ");
cout << "Original String : " << str1 << endl;
insertDemo(str1, str2);
return 0;
}
map, vector sort
#include <iostream>
#include <map>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
// vectors,lists can compare as the datatype of pair
// call compare as a function pointer
bool compare(const pair<int, int> p1, const pair<int,int> p2)
{
if (p1.second == p2.second)
{
return p1.first > p2.first;
}
return p1.second < p2.second;
}
// struct compare needs call vecCmp():
// it will also return function pointers since () overloading in this structure
struct vecCmp
{
bool operator() (const pair<int, int> p1, const pair<int,int> p2)
{
if (p1.second == p2.second)
{
return p1.first > p2.first;
}
return p1.second < p2.second;
}
};
// can only compare keys in maps, parameters is the type of keys
struct cmp
{
bool operator() (const int& p1, const int& p2)
{
return p1 > p2;
}
};
int main()
{
// sort by keys: less<int> by default, or greater<int>
// or write a struct with bool operator() () {} function inside
//map<int,int,cmp> hash = {100,4},{103,5},{108,5},{102,5};
map<int,int>::iterator it = hash.begin();
vector<pair<int,int>> vec(hash.begin(), hash.end());
for (auto item: hash)
{
cout << item.first << ":" << item.second << endl;
}
// we cannot sort map by values directly since it is a key-value related container
// first, initial a vector<pair<T1, T2>> by map.begin(), map.end()
sort(vec.begin(),vec.end(), vecCmp());
for (auto item: vec)
{
cout << item.first << ":" << item.second << endl;
}
return 0;
}
